In the first 2 quarters of FY 2012, the FACS Core Lab provided service to 26 NCI labs or branches and 2 other institutes. From these labs there were 65 principal investigators using the FACS Core Facility. These labs , with the number of principal investigators and the number of individuals using the FACS Core in parentheses, are: ATC-Gaithersburg (1 principal investigator, 1 user), CCBB (4,13), Dermatology Br (1,1), Genetics Br (3,4), HAMB (1,1), LBMB (2,3), LCB (2,3), LCBG (8,25), LCMB (4,14), LCO (2,5), LCP (1,2), LEC (1,4), LGI (1,7), LHC (2,8), LICB (2,13), LM (3,6), LMB (5,13), LMP (3,6), LP (2,2), LRBGE (3,3), MBTL (1,2), MOB (4,6), OD (1,1), POB (1,3), ROB (3,5), Surg Br (2,2), NHLBI (1,1), and NIDCR (1,2). From these labs, 156 scientists have used the FACS Core. Identifying and studying cancer stem cells are one of the major research areas of the FACS Core lab users. A number of NCI labs are using flow cytometry and fluorescence-activated cell sorting to identify and sort the cancer stem cell by membrane antigen expression using monoclonal antibodies or with a functional assay involving active membrane substrate transport. Investigators in CCBB, MBTL, LEC, LHC, and LCBG are studying cancer stem cells from breast, ovarian, hepatic, thyroid, pancreatic and lung carcinomas. The LSRII flow cytometer, the special order FACS Aria, and the MoFlo Astrios cell sorter are frequently used for these assays.Transfection of cells with genes expressing fluorescent reporters is a technique used by the majority of labs using the FACS Core. The FACS Core cytometers and cell sorters have been equipped with specific lasers to allow detection and sorting of cells labeled with any of the green, yellow, blue and red fluorescent proteins or with combinations of these fluorescent reporters. Sorted transfected cells are used to prepare protein, DNA, and RNA that can be used in Western blotting and microarrays. Sorted cells are also used to determine effects of siRNA, to look at signaling proteins, or may be further passaged to create stable cell lines. Fluorescent reporter proteins may also be linked to luciferase. Tumor cell lines have then been sorted based on their expression of green or red fluorescent protein to establish cell lines with high levels of luciferase. These cell lines have then been used to establish tumors in mice and to image metastasis. Flow cytometry is also frequently used for looking at cell growth (cell cycle analysis) and mechanisms of cell death (apoptosis) to examine actions of cancer drugs.Thirteen publications have been published so far this year that include work done in the FACS Core and acknowledge assistance of the FACS Core staff. These publications were authored by investigators in CCBB, Genetics Br, LCBG, LCMB, LCO, LCP, LEC, LHC, POB and ROB.